Steam power plant including a forced flow steam generator and a reheater



Oct. 11, 1966 w, AUGSB RGER 3,277,51

STEAM POWER PLANT INCLUDING A FORCED FLOW STEAM GENERATOR AND A REHEATER Filed July 20, 1964 Jnvemor: W/ILTER flueszunsc K United States Patent 3,277,651 STEAM POWER PLANT INCLUDING A FORCED FLOW STEAM GENERATOR AND A REHEATER Walter Augsburger, Hettlingen, Zurich, Switzerland, as-

signor to Sulzer Brothers Limited, Winterthur, Switzer land, a corporation of Switzerland Filed July 20, 1964, Ser. No. 383,641 Claims priority, application Switzerland, July 23, 1963, 9,193/ 63 2 Claims. (Cl. 60-73) The present invention relates to a steam power plant including a forced flow steam generator, a steam power engine subdivided at least into a high pressure part and a low pressure part with a reheater therebetween, a valved by-pass conduit connected to the tube system of the steam generator, a water separator, a pipe connecting the steam space of the latter to the conduit connecting the high pressure part of the power engine to the reheater, a valved pipe connected to the conduit connecting the reheater to the low pressure part of the power engine, and terminating in the live steam pipe or in the inlet of the high pressure part of the power engine, and a valved pipe connected to the outlet of the high pressure part of the power engine.

Such an arrangement is known in which the valved by-pass connected to the tube system of the steam generator is connected with the conduit connecting the high pressure part of the power engine with the reheater and which by-pass pipe continues into the water separator. The latter forms a starting-up container and also a feedwater container. The by-pass pipe which continues into the separator is provided with an additional valve and terminates below the water level of the starting-up container. The pipe connected to the steam space of the starting-up container is also provided with a valve. There is a valve in the conduit connecting the high pressure part of the power engine to the reheater, said last mentioned valve being placed between the connection of the pipe for removing steam from the steam space of the starting up container and the pipe connecting the high pressure part to the reheater and the connection of the conduit connecting the high pressure part to the reheater and the by-pass pipe which continues in the starting-up container.

It is an object of the present invention to provide a steam power plant including a forced flow steam generator which can be started up quickly and more economically, i.e. with less fuel consumption than the aforedescribed conventional plant and which is also simpler and whose first cost is lower.

In the arrangement according to the invention, in addition to the water separator, a feedwater container is provided wherein a lower pressure prevails than in the separator, the valved pipe connected to the outlet of the high pressure part of the power engine terminating in a degasifier. In the arrangement according to the invention the water separator is interposed in the bypass pipe upstream of the connection of the by-pass pipe to the conduit connecting the high pressure part to the reheater.

When starting the plant according to the invention the expansion pressure in the water separator is higher than that in the conventional plant, because the feedwater container is separate from the water separator and is under -a pressure which is lower than the pressure in the water separator. Therefore, in the arrangement according to the invention, steam can be raised quicker than in the conventional arrangement which steam can be used for warming up and starting the power engine. With the arrangement according to the invention it is not necessary to simultaneously warm up the water in 3,277,651 Patented Oct. 11, 1966 the feedwater container. Since the valved pipe connected to the outlet of the high pressure part of the power engine terminates in the degasifier the steam leaving the high pressure part during the start-up period and the heat contained therein is returned without loss to the feedwater circuit. The arrangement according to the invention is simpler particularly because is requires less shutoff valves than the conventional arrangements.

In a modification of the invention steam production can be still more accelerated when starting up the plant by connecting the by-pass pipe to the steam space of the water separator. In this arrangement it is not necessary that the liquid content of the separator is first heated by steam.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in connection with the accompanying drawing, the one figure of which is a diagrammatic layout of a steam power plant according to the invention.

Referring more particularly to the drawing, numeral 1 designates a forced flow steam generator having a plurality of tubular heating sections, namely, an economizer 2, an evaporator 3, a superheater 4 and a reheater 5. The heating sections 2, 3 and 4 are connected in series relation with respect to the flow of the operating medium. The superheater 4 is connected to the high pressure part 9 of a steam turbine plant by means of a live steam pipe 7 wherein a valve 8 is arranged. The steam turbine plant has a low pressure part 15 which, together with the high pressure part 9, drives an electric generator 36. The high pressure part 9 is connected to the reheater 5 through a pipe 12 containing a check valve 10 and a shut-off valve 11. The latter may be omitted in certain cases. The reheater 5 is connected to the low pressure part of the turbine plant by means of a pipe 13 in which a shutoif valve 14 is provided. The low pressure part 15 is connected to a condenser 16 which is connected through a pipe 37 to .a feedwater container 19 which is provided with a degasifier 45. A condensate pump 17 and two preheaters 18 are interposed in the pipe 37, the preheaters being heated in the conventional manner, not shown, by steam bled from the turbine plant. The feedwater container 19 is connected to the economizer 2 through a pipe 38. The latter contains a feed pump 35 and a preheater 39 which is heated by steam bled from the turbine in the conventional manner, not shown.

A by-pass conduit 40 is connected to the live steam pipe 7 and is provided with a pressure-maintaining and shut-off valve 20, the conduit 40 terminating in the steam space of a water separator 21. The latter is provided with a water level control 22 actuating a valve 41 controlling the removal of water from the separator 21. A pipe 42 is connected to the steam space of the separator and terminates in the pipe 12 downstream of the valve 11. Upstream of the valve 14 the pipe 13 is connected by means of a pipe 23 provided with a shut-off valve 24 to the condenser 16. A pipe 30 connected to the degasifier 45 terminates in the pipe 23 between the valve 24 and the condenser 16. A safety valve 31 is provided in the pipe 30.

Upstream of the connection of the pipe 23 a pipe 25 is connected to the pipe 13. A shut-off valve 27 and a check valve 29 are interposed in the pipe 25 which terminates in the live steam pipe 7 downstream of the valve 8. If desired, the valve 27 may be omitted. A pipe 26 is connected to the pipe 12 between the outlet of the high pressure turbine part 9 and the check valve 10, the

pipe 26 containing a shut-E valve 28 and terminating in the container 19 which is provided with the degasifier 45. By means of the pipes 25 and 26 the operating medium may be caused to pass through the reheater before entering the high pressure turbine part 9. This arrangement is of advantage at certain operating periods, as when starting or shutting down the plant or at standby operation of the plant. In addition to the live steam valve 8 a valve 8 is provided whose flow area is smaller than that of the valve 8 and which is interposed in a pipe 43 connecting the live steam pipe 7 upstream of the valve 8 to the pipe 25 downstream of the check valve 29. This arrangement affords by-passing of the valve 8.

During normal operation of the steam power plant the feed pump 35 draws feedwater from the container 19 and forces the feedwater through the feed pipe 38 and the preheater 39 into the heating sections 2 to 4. The steam generated in the evaporator 3% is superheated in the superheater 4 and conducted through the pipe 7 to the high pressure turbine part 9. After partial expansion in the high pressure turbine part the steam flows through the pipe 12 into the reheater 5 and therefrom through the pipe 13 into the low pressure turbine part 15 where it is expanded to the condenser pressure. The condensate resulting from the condensation of the steam in the condenser 16 is pumped by means of the condenser pump 17 into the container 19.

The starting operation which can be etfected quickly and economically by the arrangement according to the invention is as follows:

The live steam valve 8 and the valve 8' are closed as Well as the shut-off valves 11, 14, 27 and 28. The pressure-maintaining valve 20 and the shutoff valve 24 are open. The feed pump 35 forces operating medium through the heating sections 2 to 4 and through the bypass pipe 40 into the water separator 21 wherefrom the feedwater is returned in the conventional manner by means not shown to the feedwater container 19. The fire is now lighted and adjusted to about 10% of full load. The pressure-maintaining valve 20 is so adjusted that it maintains such pressure in the heating sections 2 to 4 that evaporation is prevented in these heating sections. During warming up the pressure maintained by the valve 20 may be higher than the normal pressure at full-load operation. The water flowing through the heating sections 2 to 4 and heated therein expands and is at least partly evaporated in the pressure-maintaining valve 20. The so produced steam is separated in the water separator 21 from the water and conducted through the pipes 42 and 12 into the reheater whereby the reheater is cooled and the steam is superheated. For a short time the operating medium passes now through the pipes 13 and 23 into the condenser 16. When the steam in the pipe 13 is of the desired quality the shut-01f valves 27 and 28 are opened and the valve 24 is closed. The steam leaving the reheater 5 now passes through the pipes 25 and 7 into the high pressure turbine part 9 and therefrom through the pipe 26 into the container 19 and the degasifier 45. The high pressure part of the turbine is now heated whereby there is a considerable pressure drop in the high pressure turbine part. The outlet of the latter is therefore considerably less heated than the inlet as is also the case when the high pressure turbine part is in normal operation.

The low pressure part 15 of the turbine may be warmed up simultaneously with starting heating of the high pressure part 9. In this case the valve 14 is opened simultaneously with the opening of the valves 27 and 28 whereby the parts 9 and 15 of the turbine plant are arranged in parallel relation with respect to the flow of steam therethrough.

After sufficient heating of the high presssure turbine part 9 and of the low pressure turbine part 15 the load of the turbine plant is increased and the electric generator 36 is connected to the power distributing system while the heat supply is at first maintained at about 10% of full load.

After rise of the temperature of the operating medium' that the heating section 4 operates at least partly as superheater the valve 11 is opened and the valve 8' is opened slowly whereby the resulting pressure drop automatically closes the pressure-maintaining valve 20 to a corresponding extent. The high pressure turbine part 9 now receives superheated steam directly from the live steam pipe 7. Part of this superheated steam comes through the valve 8'. The other part flows through the by-pass pipe 40, the now dry water separator 21, the reheater 5, and the pipe 25. Feedwater supply and heat supply may now be increased.

If the load on the steam generator continues to increase, the valve 8 is opened in addition to or in lieu of the valve 8. This causes a drop of the pressure in the pipe 7 upstream of the valve 8 and automatic closing of the pressure-maintaining valve 20. The valve 27 is now also closed and the flow of the operating medium through the plant is normal. The plant is now ready to be brought up to full load in the conventional manner.

The arrangement according to the invention is also well suited for shutting down the plant and for low-load operation. The steps described for starting up the plant are performed in the opposite sequence when the plant is shut down whereby the turbine plant can be quickly cooled without danger by quick reduction of the fuel supply. This is of advantage if the turbine plant is damaged, because the turbine housing can be opened sooner than is possible with conventional arrangements. The standstill periods of the turbine plant are therefore considerably shortened.

It is obvious that the plant according to the invention may have a power engine. subdivided into three parts whereby a flue-gas-heated reheater is arranged between the high pressure part and the medium pressure part and a further flue-gas-heated reheater is arranged between the medium pressure part and the low pressure part, the last mentioned reheater being upstream of the high pressure part or of the medium pressure part of the power engine during start-up and similar operating conditions.

In the shown example of the invention is the water volume of the degasifier larger enough to serve simultaneously as feedwater container. It is possible to separate the feedwater container and the degasifier. In such a case is placed between the feed pump 35 and the container 19 of the degasifier 45 an additional container for the feedwater.

I claim: 7

1. In a steam power plant comprising a forced flow steam generator, a high pressure turbine, a live steam pipe connecting said steam generator and said high pressure turbine, a low pressure turbine, a reheater, a first pipe connecting said high pressure turbine to said reheater, a second pipe connecting said reheater to said low pressure turbine, a by-pass conduit connected to said steam generator for receiving operating medium therefrom, a valve in said by-pas's conduit, a water separator connected to said by-pass conduit downstream of said valve, a third pipe connecting the steam space of said separator to said first pipe, a first valved conduit connecting said second pipe to said live steam pipe, and a second valved conduit connected to the outlet of said high pressure turbine:

a degasifier,

said second valved conduit terminating in said degas- 2. In a steam power plant as defined in claim 1 and wherein said by-pass conduit is connected to the steam space of said separator.

No references cited.

MARTIN P. SCHWADRON, Primary Examiner.

R. R. BUNEVICH, Assistant Examiner. 

1. IN A STEAM POWER PLANT COMPRISING A FORCED FLOW STEAM GENERATOR, A HIGH PRESSURE TURBINE, A LIVE STEAM PIPE CONNECTING SAID STEAM GENERATOR AND SAID HIGH PRESSURE TURBINE, A LOW PRESSURE TURBINE, A REHEATER, A FIRST PIPE CONNECTING SAID HIGH PRESSURE TURBINE TO SAID REHEATER, A SECOND PIPE CONNECTING SAID REHEATER TO SAID LOW PRESSURE TURBINE, A BY-PASS CONDUIT CONNECTED TO SAID STEAM GENERATOR FOR RECEIVING OPERATING MEDIUM THEREFROM, A VALVE IN SAID BY-PASS CONDUIT, A WATER SEPARATOR CONNECTED TO SAID BY-PASS CONDUIT DOWNSTREAM OF SAID VALVE, A THIRD PIPE CONNECTING THE STEAM SPACE OF SAID SEPARATOR TO SAID FIRST PIPE, A FIRST VALVED CONDUIT CONNECTING SAID SECOND PIPE TO SAID LIVE STEAM PIPE, AND A SECOND VALVED CONDUIT CONNECTED TO THE OUTLET OF SAID HIGH PRESSURE TURBINE: A DEGASIFIER, SAID SECOND VALVED CONDUIT TERMINATING IN SAID DEGASIFIER. 